JP4367923B2 - Separator material and manufacturing method thereof - Google Patents
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- JP4367923B2 JP4367923B2 JP2004123214A JP2004123214A JP4367923B2 JP 4367923 B2 JP4367923 B2 JP 4367923B2 JP 2004123214 A JP2004123214 A JP 2004123214A JP 2004123214 A JP2004123214 A JP 2004123214A JP 4367923 B2 JP4367923 B2 JP 4367923B2
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- 239000000463 material Substances 0.000 title claims description 41
- 238000004519 manufacturing process Methods 0.000 title claims description 11
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- 239000004745 nonwoven fabric Substances 0.000 claims description 156
- 239000007789 gas Substances 0.000 claims description 138
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims description 57
- 239000011737 fluorine Substances 0.000 claims description 57
- 229910052731 fluorine Inorganic materials 0.000 claims description 57
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 claims description 46
- 229920001410 Microfiber Polymers 0.000 claims description 44
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- 125000004429 atom Chemical group 0.000 description 31
- 125000000524 functional group Chemical group 0.000 description 26
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- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 6
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- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 6
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- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 5
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- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 5
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- 239000000203 mixture Substances 0.000 description 5
- 229920000098 polyolefin Polymers 0.000 description 5
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 4
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 4
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
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- OJIJEKBXJYRIBZ-UHFFFAOYSA-N cadmium nickel Chemical compound [Ni].[Cd] OJIJEKBXJYRIBZ-UHFFFAOYSA-N 0.000 description 2
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- 239000001257 hydrogen Substances 0.000 description 2
- 238000005342 ion exchange Methods 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- QELJHCBNGDEXLD-UHFFFAOYSA-N nickel zinc Chemical compound [Ni].[Zn] QELJHCBNGDEXLD-UHFFFAOYSA-N 0.000 description 2
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- HNSDLXPSAYFUHK-UHFFFAOYSA-N 1,4-bis(2-ethylhexyl) sulfosuccinate Chemical compound CCCCC(CC)COC(=O)CC(S(O)(=O)=O)C(=O)OCC(CC)CCCC HNSDLXPSAYFUHK-UHFFFAOYSA-N 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
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- RZXDTJIXPSCHCI-UHFFFAOYSA-N hexa-1,5-diene-2,5-diol Chemical compound OC(=C)CCC(O)=C RZXDTJIXPSCHCI-UHFFFAOYSA-N 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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- QPJSUIGXIBEQAC-UHFFFAOYSA-N n-(2,4-dichloro-5-propan-2-yloxyphenyl)acetamide Chemical compound CC(C)OC1=CC(NC(C)=O)=C(Cl)C=C1Cl QPJSUIGXIBEQAC-UHFFFAOYSA-N 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
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- 239000011116 polymethylpentene Substances 0.000 description 1
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- 235000020679 tap water Nutrition 0.000 description 1
- ZSDSQXJSNMTJDA-UHFFFAOYSA-N trifluralin Chemical compound CCCN(CCC)C1=C([N+]([O-])=O)C=C(C(F)(F)F)C=C1[N+]([O-])=O ZSDSQXJSNMTJDA-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
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- Electric Double-Layer Capacitors Or The Like (AREA)
- Cell Separators (AREA)
Description
本発明は、アルカリ二次電池、リチウムイオン二次電池、電気二重層キャパシタ、コンデンサー等の電気化学素子、又はイオン交換セパレータ（イオンキャッチャー）等に用いられるセパレータ材料に関する。特に、ニッケル−カドミウム電池、ニッケル−亜鉛電池、ニッケル−水素電池等のアルカリ二次電池用途において、電解液保持性が高く、耐ショート性が高く、電池の内部抵抗抑制効果及び自己放電抑制効果が高いセパレータ材料に関する。 The present invention relates to a separator material used for an electrochemical element such as an alkaline secondary battery, a lithium ion secondary battery, an electric double layer capacitor, a capacitor, or an ion exchange separator (ion catcher). In particular, in alkaline secondary battery applications such as nickel-cadmium batteries, nickel-zinc batteries, nickel-hydrogen batteries, etc., the electrolyte retention is high, the short circuit resistance is high, and the internal resistance suppression effect and self-discharge suppression effect of the battery are high. Related to high separator material.
従来から、電池セパレータ用途において、フッ素ガス処理を施した不織布が提案されている。 Conventionally, a nonwoven fabric subjected to fluorine gas treatment has been proposed for battery separator applications.
特許文献１には、繊維径１〜５０μｍの繊維を５０重量％含有するポリオレフィン系不織布をフッ素（０．０１〜８容量％）、酸素（０．１〜９５容量％）及び二酸化硫黄（１〜９５容量％）を含有する混合ガスと接触させる表面処理方法が提案されている。上記方法により得られる電池セパレータは、ＥＳＣＡにて測定した炭素に対する硫黄の元素組成比（Ｓ／Ｃ）が０．００１〜０．５０、炭素に対するフッ素の元素組成比（Ｆ／Ｃ）が０．２〜１．０、硫黄に対する酸素の元素組成比（Ｏ／Ｓ）が４．５０〜１０００を満足するものであることが開示されている。しかし、混合ガスで処理すると、硫黄含有官能基が付与しにくく、電池に組み込んだときに自己放電を抑制することが困難であった。 In Patent Document 1, a polyolefin-based nonwoven fabric containing 50% by weight of a fiber having a fiber diameter of 1 to 50 μm is made of fluorine (0.01 to 8% by volume), oxygen (0.1 to 95% by volume), and sulfur dioxide (1 to 1%). There has been proposed a surface treatment method for contacting with a mixed gas containing 95% by volume). In the battery separator obtained by the above method, the elemental composition ratio (S / C) of sulfur to carbon measured by ESCA is 0.001 to 0.50, and the elemental composition ratio of fluorine to carbon (F / C) is 0.00. 2 to 1.0, and the elemental composition ratio (O / S) of oxygen to sulfur satisfies 4.50 to 1000. However, when treated with a mixed gas, it is difficult to impart a sulfur-containing functional group, and it is difficult to suppress self-discharge when incorporated in a battery.
特許文献２には、ポリオレフィン系繊維を主体とする不織布を、亜硫酸含有ガス（０．５〜１０ｖｏｌ％）に接触させ、次いで一部の亜硫酸含有ガスを排気し、フッ素含有ガス（０．１〜１０ｖｏｌ％）を導入して複圧し、フッ素含有ガスを接触させる電池セパレータの製造方法が提案されている。しかし緻密な不織布を処理しようとしたとき、不織布の内部まで十分にガス処理できない場合があった。
近年、二次電池の高容量化に伴い、低厚み、低目付のセパレータが要求されている。そして、セパレータを低目付にするのに、極細繊維を含む不織布が用いられていた。しかし、極細繊維（特に４μｍ以下）を用いた不織布を親水化処理すると、不織布表面が選択的に処理されて内部まで処理するのが困難であった。そのため、十分な電池性能が得られなかった。 In recent years, with the increase in capacity of secondary batteries, a separator having a low thickness and a low basis weight has been demanded. And the nonwoven fabric containing an ultrafine fiber was used to make a separator a low basis weight. However, when a nonwoven fabric using ultrafine fibers (especially 4 μm or less) is subjected to a hydrophilic treatment, it is difficult to treat the nonwoven fabric surface selectively to the inside. Therefore, sufficient battery performance could not be obtained.
本発明は、前記従来の問題を解決するため、極細繊維を含む不織布を用いて、不織布の内部に存在する繊維の表面まで均一に親水化処理できるセパレータ材料とその製造方法を提供する。 In order to solve the above-described conventional problems, the present invention provides a separator material that can be uniformly hydrophilized to the surface of the fiber existing inside the nonwoven fabric by using a nonwoven fabric containing ultrafine fibers, and a method for producing the separator material.
本発明のセパレータ材料は、繊維径が４μｍ以下の極細繊維と熱接着性繊維を含む不織布で構成されたセパレータ材料であって、前記熱接着性繊維の少なくとも一部が扁平化しており、前記不織布は、電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対するフッ素原子数（Ｆ）の比（Ｆ／Ｃ）が、１×１０-2以上２０×１０-2以下の範囲内にあり、前記不織布は、下記（１）〜（３）を満たすことを特徴とする。
（１）電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Eが、１×１０-2以上１０×１０-2以下の範囲内にある。
（２）前記不織布は、フラスコ燃焼法により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Bが、０．１×１０-3以上０．５×１０-3以下の範囲内にある。
（３）前記（Ｓ／Ｃ）Eと（Ｓ／Ｃ）Bの比［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］が、１００以上２５０以下の範囲内にある。
The separator material of the present invention is a separator material composed of a nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less and thermal adhesive fibers , wherein at least a part of the thermal adhesive fibers are flattened, and the nonwoven fabric Has a ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) measured by electron spectroscopy (ESCA) with an X-ray extraction angle of 45 degrees is 1 × 10 −2 or more 20 It exists in the range of * 10 <-2> or less, The said nonwoven fabric satisfy | fills following (1)-(3), It is characterized by the above-mentioned.
(1) Ratio (S / C) of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by an electron spectroscopy (ESCA) with an X-ray extraction angle of 45 degrees E is 1 × 10 −2 It is in the range of 10 × 10 −2 or less.
(2) The nonwoven fabric has a ratio (S / C) B of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by a flask combustion method of 0.1 × 10 −3 or more and 0.5 × 10 -3 or less.
(3) the (S / C) E and (S / C) ratio of B [(S / C) E / (S / C) B] is in the range of 100 to 250 or less.
本発明のセパレータ材料の製造方法は、繊維径が４μｍ以下の極細繊維と熱接着性繊維を含み、前記熱接着性繊維の少なくとも一部が扁平化している繊維ウェブまたは不織布を、密封された反応器に入れ、不活性ガス雰囲気下、減圧に保持した状態で亜硫酸含有ガスを前記反応器に導入して前記繊維ウェブまたは前記不織布を巻き出しながら繊維表面と接触反応させ、前記亜硫酸含有ガスが存在する状態でフッ素含有ガスを前記反応器に導入して、前記亜硫酸含有ガスと前記フッ素含有ガスの混合ガスを繊維表面と接触反応させることを特徴とする。
Method for producing a separator material of the present invention, the fiber diameter is seen contains the following ultrafine fibers and the thermally adhesive fiber 4 [mu] m, the fiber web or nonwoven least part of the thermal bonding fibers are flattened, sealed Put in a reactor and introduce a sulfurous acid-containing gas into the reactor in an inert gas atmosphere while maintaining a reduced pressure to cause contact with the fiber surface while unwinding the fiber web or the nonwoven fabric. A fluorine-containing gas is introduced into the reactor in the existing state, and a mixed gas of the sulfurous acid-containing gas and the fluorine-containing gas is brought into contact with the fiber surface.
本発明は、繊維径が４μｍ以下の極細繊維を含む不織布をまず亜硫酸含有ガスと減圧下で反応させ、次いで前記亜硫酸含有ガスを残存させた状態でフッ素含有ガスと反応させるというバッチ式多段処理することにより、不織布の内部に存在する繊維の表面まで均一に親水化したセパレータ材料とその製造方法を提供できる。これにより、例えば電池セパレータにしたときは、電池の充放電時に生成してくるデンドライドに対する耐ショート性が高い二次電池を得ることができる。また、本発明のセパレータ材料は、繊維径が４μｍ以下の極細繊維を含む緻密な不織布であるにもかかわらず、不織布内部にまで硫黄含有官能基が付与されているので、電池の充放電を繰り返した時に、電解液が不織布の厚さ方向での偏在することを抑制することができ、電解液の部分的な液枯れ等がなくなり、ひいては電池の内部抵抗が低い二次電池を得ることができる。 In the present invention, a non-woven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less is first reacted with a sulfurous acid-containing gas under reduced pressure, and then reacted with a fluorine-containing gas with the sulfurous acid-containing gas remaining. Thus, it is possible to provide a separator material that is uniformly hydrophilized up to the surface of the fibers existing inside the nonwoven fabric, and a method for producing the separator material. Thereby, for example, when a battery separator is used, it is possible to obtain a secondary battery having high short-circuit resistance to dendrites generated during charging / discharging of the battery. Moreover, although the separator material of the present invention is a dense nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less, since the sulfur-containing functional group is imparted to the inside of the nonwoven fabric, the battery is repeatedly charged and discharged. The electrolyte solution can be prevented from being unevenly distributed in the thickness direction of the nonwoven fabric, and the electrolyte solution can be partially withered, resulting in a secondary battery with low battery internal resistance. .
従来のガス接触法で極細繊維を用いるなどした緻密な不織布を処理すると、硫黄含有官能基が不織布表面に集中して、不織布全体からすると表面に偏在していることが判り、本発明の製造方法を採ることにより、不織布内部にまで硫黄含有官能基を付与することができることを見出した。 When processing a dense nonwoven fabric using ultrafine fibers in the conventional gas contact method, it can be seen that sulfur-containing functional groups are concentrated on the surface of the nonwoven fabric and unevenly distributed on the surface of the nonwoven fabric as a whole. It was found that the sulfur-containing functional group can be imparted to the inside of the nonwoven fabric by adopting
本発明は、繊維径が４μｍ以下の極細繊維を含む不織布であって、前記不織布は、電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対するフッ素原子数（Ｆ）の比（Ｆ／Ｃ）が、１×１０-2以上２０×１０-2以下の範囲内にあり、前記不織布は、下記（１）〜（３）を満たすセパレータ材料である。
（１）電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Eが、１×１０-2以上１０×１０-2以下の範囲内にある。
（２）フラスコ燃焼法により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Bが、０．１×１０-3以上０．５×１０-3以下の範囲内にある。
（３）（Ｓ／Ｃ）Eと（Ｓ／Ｃ）Bの比［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］が、１００以上２５０以下の範囲内にある。
The present invention is a nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less, and the nonwoven fabric is fluorine with respect to the number of carbon atoms (C) measured by an X-ray extraction angle of 45 degrees using electron spectroscopy (ESCA). The ratio (F / C) of the number of atoms (F) is in the range of 1 × 10 −2 or more and 20 × 10 −2 or less, and the nonwoven fabric is a separator material that satisfies the following (1) to (3). .
(1) Ratio (S / C) of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by an electron spectroscopy (ESCA) with an X-ray extraction angle of 45 degrees E is 1 × 10 −2 It is in the range of 10 × 10 −2 or less.
(2) Ratio of sulfur atom number (S) to carbon atom number (C) measured by flask combustion method (S / C) B is 0.1 × 10 −3 or more and 0.5 × 10 −3 or less. Is in range.
(3) (S / C) E and (S / C) ratio of B [(S / C) E / (S / C) B] is in the range of 100 to 250 or less.
本発明のセパレータ材料は、繊維径が４μｍ以下の極細繊維を含む不織布であり、電池の充放電時に生成してくるデンドライドに対する耐ショート性が高い二次電池を得ることができる。 The separator material of the present invention is a nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less, and a secondary battery having high short-circuit resistance against dendrites generated during charging / discharging of the battery can be obtained.
さらに、本発明のセパレータ材料は、繊維径が４μｍ以下の極細繊維を含む緻密な不織布であるにもかかわらず、不織布内部にまで硫黄含有官能基が付与されているので、電池の充放電を繰り返した時に、電解液が不織布の厚さ方向での偏在することを抑制することができ、電解液の部分的な液枯れ等がなくなり、ひいては電池の内部抵抗が低い二次電池を得ることができる。 Furthermore, although the separator material of the present invention is a dense nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less, since the sulfur-containing functional group is imparted to the inside of the nonwoven fabric, the battery is repeatedly charged and discharged. The electrolyte solution can be prevented from being unevenly distributed in the thickness direction of the nonwoven fabric, and the electrolyte solution can be partially withered, resulting in a secondary battery with low battery internal resistance. .
本発明において、極細繊維の繊維径は０．５μｍ以上４μｍ以下が好ましい。より好ましい極細繊維の繊維径は、１．５μｍ以上である。より好ましい極細繊維の繊維径は、３．５μｍ以下である。繊維径が４μｍを超えると、電池の高容量下に伴い低目付、低厚みの不織布としたとき、不織布の緻密性が低下して、電池に組み込んだときの耐ショート性が低下する傾向にある。繊維径が０．５μｍ未満は、製造が難しくコストが高くなる傾向となる。繊維径は、繊維断面が円形の場合、直接的にその直径を測定した値でもって単繊維の直径とし、繊維断面が異形の場合、単繊維の繊度を測定し、この単繊維が円形と仮定して下記式で得られる直径で表すことができる。
繊維径（μｍ）＝｛√４×√Ｄ×１０3｝／｛√π×√１００００×√ρ｝
Ｄ：単繊維の繊度（ｄｔｅｘ）
ρ：単繊維を構成する樹脂の密度（ｇ／ｃｍ3）
本発明の不織布の比表面積は、０．７ｍ2／ｇ以上１．５ｍ2／ｇ以下の範囲が好ましい。より好ましい不織布の比表面積は、０．９ｍ2／ｇ以上である。より好ましい不織布の比表面積は１．２ｍ2／ｇ以下である。不織布の比表面積は、不織布を構成する繊維の繊維径、形状、繊維同士の結合状態、集積状態等で変わる。比表面積が小さいと、フッ素処理したときに処理が繊維内部にまで浸透するため官能基が有効に作用しない場合がある。さらに、不織布の緻密性が低下することから耐ショート性が低下する場合がある。一方、比表面積が大きいと、不織布自体が緻密な構造となりすぎるため、電池内でのガス透過性が低下し、電池の内圧上昇の要因となることがある。
In the present invention, the fiber diameter of the ultrafine fiber is preferably 0.5 μm or more and 4 μm or less. A more preferable fiber diameter of the ultrafine fiber is 1.5 μm or more. The fiber diameter of the ultrafine fiber is more preferably 3.5 μm or less. When the fiber diameter exceeds 4 μm, when the nonwoven fabric has a low weight per unit area and a low thickness due to the high capacity of the battery, the density of the nonwoven fabric tends to decrease, and the short-circuit resistance when incorporated in the battery tends to decrease. . If the fiber diameter is less than 0.5 μm, the production is difficult and the cost tends to increase. When the fiber cross section is circular, the diameter of the single fiber is determined by directly measuring the diameter of the fiber. When the fiber cross section is irregular, the fineness of the single fiber is measured and the single fiber is assumed to be circular. And can be expressed by the diameter obtained by the following formula.
Fiber diameter (μm) = {√4 × √D × 10 3 } / {√π × √10000 × √ρ}
D: Fineness of single fiber (dtex)
ρ: Density of resin constituting single fiber (g / cm 3 )
The specific surface area of the nonwoven fabric of the present invention, 0.7 m 2 / g or more 1.5 m 2 / g is preferably in a range of about. A more preferable specific surface area of the nonwoven fabric is 0.9 m 2 / g or more. A more preferable non-woven fabric has a specific surface area of 1.2 m 2 / g or less. The specific surface area of the nonwoven fabric varies depending on the fiber diameter and shape of the fibers constituting the nonwoven fabric, the bonding state between fibers, the accumulation state, and the like. If the specific surface area is small, the functional group may not work effectively because the treatment penetrates into the fiber when the fluorine treatment is performed. Furthermore, since the denseness of the nonwoven fabric decreases, the short-circuit resistance may decrease. On the other hand, if the specific surface area is large, the nonwoven fabric itself has a too dense structure, so that gas permeability in the battery is lowered, which may cause an increase in the internal pressure of the battery.
前記比表面積を満足するのに、繊維径が４μｍ以下の極細繊維を３０ｍａｓｓ％以上８０ｍａｓｓ％以下の範囲で含むことが好ましい。より好ましい極細繊維の含有量は、４０ｍａｓｓ％以上である。より好ましい極細繊維の含有量は、６０ｍａｓｓ％以下である。 In order to satisfy the specific surface area, it is preferable that ultrafine fibers having a fiber diameter of 4 μm or less are included in a range of 30 mass% to 80 mass%. A more preferable ultrafine fiber content is 40 mass% or more. A more preferable ultrafine fiber content is 60 mass% or less.
極細繊維の形状は、円形、異形、中空などいずれでもよい。単一、複合のいずれでもよい。海島型複合繊維の１成分を溶出して極細繊維を発現させる方法、分割型複合繊維を割繊させて極細繊維を発現させる方法などが挙げられ、分割型複合繊維を出発材料とすると、得られる極細繊維は扁平化されており比表面積が大きく、好ましい。 The shape of the ultrafine fiber may be any of circular, irregular, hollow and the like. Either single or composite may be used. Examples include a method of elution of one component of a sea-island type composite fiber to express an ultrafine fiber, a method of splitting a split type composite fiber to express an ultrafine fiber, and the like. Ultrafine fibers are preferred because they are flattened and have a large specific surface area.
極細繊維を形成する樹脂は、ポリエチレン、ポリプロピレン、ポリメチルペンテン、エチレン−ビニルアルコール共重合体などのポリオレフィン樹脂が好ましい。エチレン−ビニルアルコール共重合体は、親水基を有しており、電解液との親和性を向上させることができるとともに、フッ素処理したときにフッ素との反応性が高く、容易に硫黄含有官能基を付与することができるので、好ましい。 The resin forming the ultrafine fibers is preferably a polyolefin resin such as polyethylene, polypropylene, polymethylpentene, or ethylene-vinyl alcohol copolymer. The ethylene-vinyl alcohol copolymer has a hydrophilic group, can improve the affinity with the electrolytic solution, has high reactivity with fluorine when treated with fluorine, and easily contains a sulfur-containing functional group. Is preferable.
前記エチレン−ビニルアルコール共重合体におけるエチレン含有量は、２０モル％以上５０モル％以下の範囲内にあることが好ましい。より好ましいエチレン含有量の下限は、２５モル％である。より好ましいエチレン含有量の上限は、４５モル％である。エチレン含有量が２０モル％未満であると、極細繊維を得ることが困難となる場合がある。一方、エチレン含有量が５０モル％を超えると、電解液との親和性、あるいはフッ素との反応性が低下する場合がある。 The ethylene content in the ethylene-vinyl alcohol copolymer is preferably in the range of 20 mol% to 50 mol%. A more preferable lower limit of the ethylene content is 25 mol%. The upper limit of more preferable ethylene content is 45 mol%. If the ethylene content is less than 20 mol%, it may be difficult to obtain ultrafine fibers. On the other hand, if the ethylene content exceeds 50 mol%, the affinity with the electrolytic solution or the reactivity with fluorine may decrease.
前記極細繊維以外に混合される他の繊維の含有量は、２０ｍａｓｓ％以上７０ｍａｓｓ％以下の範囲であることが好ましい。より好ましい他の繊維の含有量は、４０ｍａｓｓ％以上である。より好ましい他の繊維の含有量は、６０ｍａｓｓ％以下である。他の繊維は、熱接着性繊維単独、又は熱接着性繊維と繊維強度５ｃＮ／dtex以上の高強度繊維を混合して用いることが好ましい。他の繊維における熱接着性繊維と高強度繊維との比（熱接着性繊維：高強度繊維の質量比）は、１００：０〜５０：５０であることが好ましい。より好ましい熱接着性繊維：高強度繊維の質量比は、９０：１０〜６０：４０である。熱接着性繊維が少なくなると、不織布の引張強さが不足することがある。また、高強度繊維を混合すると、電極間にセパレータ材料を積層し、又は巻回して電池を組み立てる時、電極のバリ等がセパレータ材料を突き刺した際の耐久性が高く、耐ショート性が高くなる点で好ましい。 The content of other fibers to be mixed in addition to the ultrafine fibers is preferably in the range of 20 mass% to 70 mass%. The more preferable content of other fibers is 40 mass% or more. The more preferable content of other fibers is 60 mass% or less. The other fibers are preferably used by mixing the heat-adhesive fibers alone or a mixture of the heat-adhesive fibers and high-strength fibers having a fiber strength of 5 cN / dtex or more. The ratio of heat-adhesive fibers and high-strength fibers in other fibers (mass ratio of heat-adhesive fibers: high-strength fibers) is preferably 100: 0 to 50:50. A more preferable mass ratio of heat-adhesive fiber: high-strength fiber is 90:10 to 60:40. If the heat-adhesive fibers are reduced, the tensile strength of the nonwoven fabric may be insufficient. In addition, when high strength fibers are mixed, when a battery is assembled by laminating or winding separator materials between electrodes, durability when the separator material pierces the separator material is high and short circuit resistance is high. This is preferable.
比表面積を調整すべく、前記他の繊維における繊維径は、４μｍを超え、２５μｍ以下の範囲が好ましい。より好ましい他の繊維の繊維径は、８μｍ以上であり、さらにより好ましくは１０μｍ以上である。より好ましい他の繊維の繊維径は、２０μｍ以下である。他の繊維の繊維径が小さすぎると、前記極細繊維と大差がなく、耐ショート性に効果はあるが、不織布が緻密になりすぎるため電池内での内圧が上昇する場合がある。他の繊維の繊維径が２５μｍを超えると、不織布の緻密性に劣るため、充放電時のデンドライドに対する耐ショート性に劣る場合がある。 In order to adjust the specific surface area, the fiber diameter of the other fibers is preferably more than 4 μm and not more than 25 μm. More preferably, the fiber diameter of the other fibers is 8 μm or more, and even more preferably 10 μm or more. More preferably, the fiber diameter of other fibers is 20 μm or less. If the fiber diameter of the other fibers is too small, there is no great difference from the ultrafine fibers and there is an effect on short-circuit resistance, but the nonwoven fabric becomes too dense and the internal pressure in the battery may increase. If the fiber diameter of the other fibers exceeds 25 μm, the nonwoven fabric is inferior in denseness, and may be inferior in short-circuit resistance to dendrid during charging and discharging.
前記熱接着性繊維を構成する樹脂としては、ポリエチレン、ポリプロピレン、ポリブテン−１等のホモ、コポリマーのうち少なくとも１種から選ばれるポリオレフィン樹脂であることが好ましい。特に、前記極細繊維を構成する樹脂の融点よりも１０℃以上低い融点を持つポリオレフィン樹脂は、不織布の比表面積を調整し易く、好ましい。 The resin constituting the heat-adhesive fiber is preferably a polyolefin resin selected from at least one of homo- and copolymers such as polyethylene, polypropylene, and polybutene-1. In particular, a polyolefin resin having a melting point that is lower by 10 ° C. or more than the melting point of the resin constituting the ultrafine fiber is preferable because the specific surface area of the nonwoven fabric can be easily adjusted.
前記熱接着性繊維の断面形状は、円形、異形、中空等の繊維断面を有する単一、又は複合形態が挙げられる。熱接着性繊維として、前記極細繊維を構成する樹脂の融点よりも１０℃以上低い融点を持つポリオレフィン樹脂（以下、「低融点ポリオレフィン樹脂」という）を１成分（熱接着成分）とし、前記低融点ポリオレフィン樹脂が少なくとも繊維表面の２０％を占める繊維であることが好ましい。熱接着性繊維における熱接着成分の融点が極細繊維を構成する樹脂の融点の１０℃未満であると、熱接着性繊維を溶融させたときに極細繊維も溶融してしまうので、繊維間空隙を閉塞してしまい、所望の不織布の比表面積が得られない場合がある。 Examples of the cross-sectional shape of the heat-adhesive fiber include a single shape or a composite shape having a fiber cross section such as a circular shape, an irregular shape, or a hollow shape. As the heat-adhesive fiber, a polyolefin resin (hereinafter referred to as “low-melting-point polyolefin resin”) having a melting point lower by 10 ° C. or more than the melting point of the resin constituting the ultrafine fiber is used as one component (thermoadhesive component), and the low melting point The polyolefin resin is preferably a fiber that occupies at least 20% of the fiber surface. If the melting point of the heat bonding component in the heat bonding fiber is less than 10 ° C. of the melting point of the resin constituting the fine fiber, the fine fiber also melts when the heat bonding fiber is melted. It may block | close and the specific surface area of a desired nonwoven fabric may not be obtained.
前記熱接着性繊維のうち、低融点ポリオレフィン樹脂を鞘成分とし、低融点ポリオレフィン樹脂より融点が１０℃以上高いポリオレフィン樹脂（以下、高融点ポリオレフィン樹脂という）を芯成分とする鞘芯型複合繊維は、不織布を構成する繊維を熱接着させたときの不織布の引張強さが高く、好ましい。より好ましい鞘芯型複合繊維の形態は、鞘成分と芯成分とが同心円状に配置されたものである。 Of the heat-adhesive fibers, a low-melting-point polyolefin resin is a sheath component, and a sheath-core type composite fiber having a core component of a polyolefin resin whose melting point is 10 ° C. or higher than the low-melting-point polyolefin resin (hereinafter referred to as high-melting-point polyolefin resin) is The tensile strength of the nonwoven fabric when the fibers constituting the nonwoven fabric are thermally bonded is preferable. A more preferable form of the sheath-core type composite fiber is that in which the sheath component and the core component are arranged concentrically.
具体的な鞘芯型複合繊維の組み合わせとしては、高密度ポリエチレン／ポリプロピレン、プロピレンコポリマー／ポリプロピレン等が挙げられ、特に所望の不織布の比表面積を維持しつつ、より高い不織布の引張強さを得るのであれば、鞘成分の繊維融点が１４５℃以下のエチレン−プロピレンコポリマー／ポリプロピレン、エチレン−ブテン−プロピレンコポリマー／ポリプロピレンの組み合わせが熱接着部の強力が大きく、好ましい。なお、融点はJIS-K-7121(DSC法)に準じ測定したものをいう。 Specific combinations of sheath-core type composite fibers include high-density polyethylene / polypropylene, propylene copolymer / polypropylene, and the like, in particular, to obtain a higher nonwoven fabric tensile strength while maintaining the desired specific surface area of the nonwoven fabric. If present, a combination of an ethylene-propylene copolymer / polypropylene and an ethylene-butene-propylene copolymer / polypropylene having a fiber melting point of the sheath component of 145 ° C. or less is preferable because the strength of the thermal bonding portion is large. The melting point is measured according to JIS-K-7121 (DSC method).
また、本発明のセパレータ材料は、適度な比表面積を有するとともに高い突き刺し強力の不織布を得るために、前記他の繊維として繊維強度５ｃＮ／dtex以上の高強度短繊維を含むことが好ましい。より好ましい高強度短繊維の繊維強度は、６ｃＮ／dtex以上である。前記高強度繊維を構成する樹脂としては、ポリプロピレン、超高分子量ポリエチレン等のホモ又はコポリマーなどのポリオレフィン樹脂であることが好ましい。特に、前記熱接着性繊維における熱接着成分の融点よりも１０℃以上高い融点を持つポリオレフィン樹脂を用いると、不織布の比表面積を調整し易く、好ましい。 In addition, the separator material of the present invention preferably includes high strength short fibers having a fiber strength of 5 cN / dtex or more as the other fibers in order to obtain a nonwoven fabric having an appropriate specific surface area and a high piercing strength. More preferable fiber strength of the high strength short fiber is 6 cN / dtex or more. The resin constituting the high-strength fiber is preferably a polyolefin resin such as a homo- or copolymer such as polypropylene and ultrahigh molecular weight polyethylene. In particular, it is preferable to use a polyolefin resin having a melting point higher by 10 ° C. or more than the melting point of the thermal adhesive component in the thermal adhesive fiber because the specific surface area of the nonwoven fabric can be easily adjusted.
また前記不織布は、構成する繊維のうち少なくとも一部が扁平化されていると、不織布の比表面積が増加し好ましい。さらに、扁平化された繊維を含む比表面積の大きい不織布は、フッ素ガス処理すると反応物質が不織布内部に滞留しやすく、不織布内部まで硫黄原子を含む官能基を導入しやすくなり、好ましい。 In addition, it is preferable that the nonwoven fabric has at least a part of the constituent fibers flattened because the specific surface area of the nonwoven fabric increases. Furthermore, a non-woven fabric with a large specific surface area containing flattened fibers is preferable because the reactive substance tends to stay inside the non-woven fabric when treated with fluorine gas, and a functional group containing sulfur atoms is easily introduced into the non-woven fabric.
比表面積を調整すべく、不織布は湿式抄紙法で形成されることが好ましい。さらに、湿式抄紙した後、水流交絡処理することが好ましい。 In order to adjust the specific surface area, the nonwoven fabric is preferably formed by a wet papermaking method. Furthermore, it is preferable to perform hydroentanglement after wet papermaking.
前記不織布における電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対するフッ素原子数（Ｆ）の比（Ｆ／Ｃ）は、１×１０-2以上２０×１０-2以下の範囲であり、さらに５×１０-2以上１０×１０-2の範囲内にあることが好ましい。Ｆ／Ｃは、不織布表面に付与された炭素原子数に対するフッ素原子数を示すものであり、フッ素処理の強さ（フッ素処理強度）を示す指標でもある。フッ素処理強度はフッ素ガスの処理濃度、処理時間、処理温度等により決定され、値が大きいほどフッ素処理が強い条件で行われたこととなる。強い条件でフッ素処理を施すと、硫黄含有官能基、あるいは酸素含有官能基を多く付与することができるが、繊維の内部まで必要以上に改質されるため、繊維強度が低下し、ひいては不織布強力が低下するので、Ｆ／Ｃを上記範囲内とすることにより、繊維強度の低下を抑えるとともに、繊維表面に有効量の硫黄含有官能基、あるいは酸素含有官能基を付与することができる。 The ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) measured with an X-ray extraction angle of 45 degrees using electron spectroscopy (ESCA) in the nonwoven fabric is 1 × 10 −2 or more. It is preferably in the range of 20 × 10 −2 or less, and more preferably in the range of 5 × 10 −2 or more and 10 × 10 −2 . F / C indicates the number of fluorine atoms relative to the number of carbon atoms imparted to the nonwoven fabric surface, and is also an index indicating the strength of fluorine treatment (fluorine treatment strength). The fluorine treatment intensity is determined by the treatment concentration, treatment time, treatment temperature, etc. of the fluorine gas, and the larger the value, the stronger the fluorine treatment. When fluorine treatment is applied under strong conditions, many sulfur-containing functional groups or oxygen-containing functional groups can be added. However, since the inside of the fiber is unnecessarily modified, the fiber strength decreases, and the nonwoven fabric is strong. Therefore, by setting F / C within the above range, it is possible to suppress a decrease in fiber strength and to impart an effective amount of a sulfur-containing functional group or an oxygen-containing functional group to the fiber surface.
前記不織布における電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Eは、１×１０-2以上１０×１０-2以下の範囲であり、さらに２×１０-2以上８×１０-2以下の範囲内にあることが好ましい。（Ｓ／Ｃ）Eは不織布表面に付与された硫黄原子量を示すものである。硫黄原子量は、前記フッ素処理の強さと、硫黄含有ガスの処理濃度、処理時間、処理温度等により決定される。（Ｓ／Ｃ）Eが小さいと、不織布表面に導入される硫黄含有官能基が少なくなるため、親水性が低下して電解液保持性が低下する傾向にあるだけでなく、自己放電を抑制することが困難となる場合がある。（Ｓ／Ｃ）Eが大きいと、フッ素処理が必要以上に強い条件で処理されていることとなり、繊維および不織布の劣化が激しく、不織布の引張強さが低くなる場合がある。 The ratio (S / C) E of sulfur atoms (S) to said electron spectroscopy in the nonwoven fabric (ESCA) carbon atoms, as measured by X-ray extraction angle of 45 degrees with the (C) is, 1 × 10 -2 or 10 × in the range of 10 -2 or less, preferably in a further 2 × 10 -2 or more 8 × 10 -2 within the following range. (S / C) E indicates the amount of sulfur atoms imparted to the nonwoven fabric surface. The amount of sulfur atoms is determined by the strength of the fluorine treatment, the treatment concentration of the sulfur-containing gas, the treatment time, the treatment temperature, and the like. (S / C) When E is small, sulfur-containing functional groups introduced into the nonwoven fabric surface are reduced, and thus not only the hydrophilicity tends to be lowered and the electrolyte solution retention tends to be lowered, but also self-discharge is suppressed. May be difficult. (S / C) When E is large, the fluorine treatment is performed under conditions that are stronger than necessary, and the fibers and the nonwoven fabric may deteriorate significantly, and the tensile strength of the nonwoven fabric may be lowered.
前記不織布におけるフラスコ燃焼法により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Bは、０．１×１０-3以上０．５×１０-3以下の範囲であり、０．１５×１０-3以上０．３×１０-3以下の範囲であることが好ましい。（Ｓ／Ｃ）Bは、不織布全体に付与された硫黄原子数を示すものである。（Ｓ／Ｃ）Bが少ないと、不織布全体に導入される硫黄含有官能基が少なくなるため、親水性が低下して電解液保持性が低下する傾向にあるだけでなく、自己放電を抑制することが困難となる場合がある。（Ｓ／Ｃ）Bが大きいと、フッ素処理が必要以上に強い条件で処理されていることとなり、繊維および不織布の劣化が激しく、不織布の引張強さが低くなり、ひいてはセパレータを電池に組み込む時の耐ショート性が低下する場合がある。 The ratio (S / C) B of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by the flask combustion method in the nonwoven fabric is 0.1 × 10 −3 or more and 0.5 × 10 −3 or less. The range is preferably 0.15 × 10 −3 or more and 0.3 × 10 −3 or less. (S / C) B represents the number of sulfur atoms imparted to the entire nonwoven fabric. (S / C) When there is little B , since the sulfur-containing functional group introduced into the whole nonwoven fabric decreases, not only the hydrophilicity tends to decrease and the electrolytic solution retention tends to decrease, but also self-discharge is suppressed. May be difficult. (S / C) When B is large, the fluorine treatment is performed under conditions that are stronger than necessary, and the fiber and the nonwoven fabric are severely deteriorated, the tensile strength of the nonwoven fabric is lowered, and as a result, the separator is incorporated into the battery. The short-circuit resistance may be reduced.
（Ｓ／Ｃ）Eと（Ｓ／Ｃ）Bの比［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］は、１００以上２５０以下の範囲であり、さらに１００以上２００以下の範囲であることか好ましい。［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］は、不織布表面と不織布全体の硫黄原子数を比較するものであって、言い換えれば、不織布内部までどの程度硫黄含有官能基を付与することができたかを示す指標である。値が小さいほど、不織布内部の硫黄含有官能基が多いことを示す。［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］を上記範囲とし、不織布表面と不織布内部における硫黄含有官能基の偏在を抑えることにより、電池の充放電を繰り返した時に、電解液が不織布の厚さ方向での偏在することを抑制することができ、電解液の部分的な液枯れ等がなくなるので、電池の内部抵抗が低い二次電池を得ることができる。 (S / C) E and (S / C) ratio of B [(S / C) E / (S / C) B] is in the range of 100 to 250 or less, further in the range of 100 to 200 That is preferable. [(S / C) E / (S / C) B ] compares the number of sulfur atoms between the nonwoven fabric surface and the entire nonwoven fabric, in other words, how much sulfur-containing functional groups are imparted to the interior of the nonwoven fabric. This is an index indicating whether or not It shows that there are many sulfur containing functional groups inside a nonwoven fabric, so that a value is small. When [(S / C) E / (S / C) B ] is within the above range and the uneven distribution of sulfur-containing functional groups on the nonwoven fabric surface and inside the nonwoven fabric is suppressed, when the battery is repeatedly charged and discharged, the electrolyte solution becomes the nonwoven fabric. The secondary battery with low internal resistance can be obtained because the electrolyte solution can be prevented from being unevenly distributed and the liquid electrolyte can be partially withered.
前記不織布における電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角７５度により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比を（Ｓ／Ｃ）E75としたとき、（Ｓ／Ｃ）Eと（Ｓ／Ｃ）E75の比［（Ｓ／Ｃ）E／（Ｓ／Ｃ）E75］は、１．２以上１．５以下の範囲が好ましく、さらに１．２以上１．４以下の範囲であることがより好ましい。（［（Ｓ／Ｃ）E／（Ｓ／Ｃ）E75］は、ＥＳＣＡにおけるＸ線取り出し角が異なり、Ｘ線取り出し角を４５度とした場合と、取り出し角を７５度とした場合では、取り出し角４５度に対して取り出し角７５度の方が不織布表面から約１．４倍の深さまでの硫黄原子数を測定することができる。この比が大きいほど不織布表面に存在する繊維表面の硫黄原子量が多く、繊維内部の硫黄原子量が少ないことを意味し、繊維強度を低下させることなく、有効量の硫黄含有官能基を付与することができる。 When the ratio of the number of sulfur atoms (S) to the number of carbon atoms (C) measured with an X-ray extraction angle of 75 degrees using electron spectroscopy (ESCA) in the nonwoven fabric is (S / C) E75 , (S / C) The ratio of E to (S / C) E75 [(S / C) E / (S / C) E75 ] is preferably in the range of 1.2 to 1.5, and more preferably 1.2 to 1. A range of 4 or less is more preferable. ([(S / C) E / (S / C) E75 ] is different when the X-ray extraction angle in ESCA is different and the X-ray extraction angle is 45 degrees and the extraction angle is 75 degrees. When the take-off angle is 75 degrees with respect to the angle of 45 degrees, the number of sulfur atoms from the nonwoven fabric surface to a depth of about 1.4 times can be measured. This means that the amount of sulfur atoms in the fiber is small, and an effective amount of a sulfur-containing functional group can be imparted without reducing the fiber strength.
本発明のセパレータ材料の目付は、２０ｇ／ｍ2以上１００ｇ／ｍ2以下の範囲が好ましく、さらに２０〜５０ｇ／ｍ2の範囲がより好ましい。 Basis weight of the separator material of the present invention, 20 g / m 2 or more 100 g / m 2 more preferably in the range, further a range of 20 to 50 g / m 2 is more preferable.
本発明のセパレータ材料の厚みは、２０μｍ以上２００μｍ以下の範囲が好ましく、さらに５０μｍ以上１００μｍ以下の範囲であることがより好ましい。 The thickness of the separator material of the present invention is preferably in the range of 20 μm to 200 μm, and more preferably in the range of 50 μm to 100 μm.
本発明の製造方法は、繊維径が４μｍ以下の極細繊維を含む繊維ウェブまたは不織布を準備する。前記繊維ウェブの形態は、カード法、エアレイ法等により得た乾式ウェブ、湿式法により得た湿式抄紙ウェブ等の短繊維ウェブが用いられる。なかでも前記構成繊維の繊維長が１ｍｍ以上２５ｍｍ以下の範囲で構成される湿式抄紙ウェブは、均質なウェブを得る点で好ましい。より好ましい繊維長の下限は、３ｍｍである。より好ましい繊維長の上限は、１５ｍｍである。構成繊維の繊維長が１ｍｍ未満であると、後述する水流交絡処理時に繊維が飛散して不織布の最大孔径が大きくなる傾向にあり、均質な不織布を得るのが困難となる。構成繊維の繊維長が２５ｍｍを超えると、スラリー中における繊維の分散性が悪くなって均質な不織布を得るのが困難となり、不織布の最大孔径が大きくなる傾向にある。 The production method of the present invention prepares a fiber web or nonwoven fabric containing ultrafine fibers having a fiber diameter of 4 μm or less. As the form of the fiber web, a short fiber web such as a dry web obtained by a card method, an air lay method or the like, or a wet papermaking web obtained by a wet method is used. Especially, the wet papermaking web comprised in the range whose fiber length of the said constituent fiber is 1 mm or more and 25 mm or less is preferable at the point which obtains a homogeneous web. A more preferable lower limit of the fiber length is 3 mm. A more preferable upper limit of the fiber length is 15 mm. If the fiber length of the constituent fibers is less than 1 mm, the fibers scatter during the hydroentanglement process described later, and the maximum pore diameter of the nonwoven fabric tends to increase, making it difficult to obtain a homogeneous nonwoven fabric. If the fiber length of the constituent fibers exceeds 25 mm, the dispersibility of the fibers in the slurry becomes poor and it becomes difficult to obtain a homogeneous nonwoven fabric, and the maximum pore diameter of the nonwoven fabric tends to increase.
前記湿式抄紙ウェブを得る方法としては、通常の湿式抄紙機を用いて作製することができる。湿式抄紙ウェブを得る具体的な一例としては、まず前記構成繊維を所望の範囲となるように混合し、０．０１mass％以上０．６mass％以下の範囲の濃度になるように水に分散させてスラリーを調製する。このとき、極細繊維として分割型複合短繊維を用いる場合、湿式抄紙する前工程において、少なくとも一部の分割型複合短繊維を割繊して、極細繊維を形成させておくことが好ましい。前記処理を行うことにより、極細繊維は不織布中に略均一に分散されて、適度な比表面積を有する不織布を得ることができる。上記割繊処理としては、スラリーを調整する段階における離解処理及び／又は叩解処理で処理することが挙げられる。具体的には、パルパーを用いて割繊処理すると、離解・叩解処理が同時に行われるので、好ましい。 As a method for obtaining the wet papermaking web, it can be produced using a normal wet papermaking machine. As a specific example of obtaining a wet papermaking web, first, the constituent fibers are mixed so as to be in a desired range, and dispersed in water so as to have a concentration in a range of 0.01 mass% to 0.6 mass%. Prepare a slurry. At this time, when the split-type composite short fibers are used as the ultrafine fibers, it is preferable that at least a part of the split-type composite short fibers is split to form the ultrafine fibers in the pre-process for wet papermaking. By performing the treatment, the ultrafine fibers are dispersed substantially uniformly in the nonwoven fabric, and a nonwoven fabric having an appropriate specific surface area can be obtained. Examples of the splitting process include a disaggregation process and / or a beating process in the stage of adjusting the slurry. Specifically, splitting using a pulper is preferable because disaggregation and beating processing are performed simultaneously.
次いで、前記スラリーから円網式、短網式、あるいは長網式等の湿式抄紙機を用いて湿式抄紙ウェブを作製する。このとき、円網式湿式抄紙機を用いた円網式湿式抄紙ウェブを少なくとも１層用いると、不織布縦方向の引張強さが向上し、好ましい。得られた湿式抄紙ウェブは、１層で、又は２層以上に抄き合わせて毛布等の搬送用支持体で搬送されて、シリンダードライヤー、熱ロール等公知の熱処理機を用いて、乾燥させるか、又は熱接着性繊維を含む場合、熱接着性繊維が溶融する温度より高い温度で熱処理して、繊維同士を熱接着させて湿式抄紙を得る。このとき、不織布を構成する繊維の少なくとも一部を扁平化させることが好ましい。さらに、少なくとも一部の熱接着性繊維を扁平化させて構成する繊維同士を熱接着させることが好ましい。熱接着性繊維を扁平化させて構成する繊維同士を熱接着させることにより、水流交絡処理による不織布の引張強さの低下を抑制することができ、過度に熱処理する必要がなくなるからである。熱接着性繊維を扁平化させるには、適度な加圧状態とすることがよく、例えば２０Ｎ／ｃｍ以上１００Ｎ／ｃｍ以下の範囲にある線圧で処理することが好ましい。 Next, a wet papermaking web is produced from the slurry using a wet papermaking machine such as a circular netting type, a short netting type or a long netting type. At this time, it is preferable to use at least one layer of a net-type wet papermaking web using a net-type wet papermaking machine because the tensile strength in the longitudinal direction of the nonwoven fabric is improved. The obtained wet papermaking web is made up of one layer or two or more layers and conveyed on a carrier such as a blanket and dried using a known heat treatment machine such as a cylinder dryer or a hot roll. In the case of including a heat-adhesive fiber, heat treatment is performed at a temperature higher than the temperature at which the heat-adhesive fiber melts, and the fibers are thermally bonded to obtain a wet papermaking. At this time, it is preferable to flatten at least a part of the fibers constituting the nonwoven fabric. Furthermore, it is preferable to thermally bond the fibers formed by flattening at least some of the heat-bondable fibers. This is because by reducing the tensile strength of the nonwoven fabric due to the hydroentanglement process, it is not necessary to heat treat excessively by thermally bonding the fibers formed by flattening the heat-adhesive fibers. In order to flatten the heat-adhesive fiber, it is preferable to use an appropriate pressure state. For example, it is preferable to treat with a linear pressure in the range of 20 N / cm to 100 N / cm.
本発明の一実施例の湿式抄紙した後の不織布構造について、図１に電子顕微鏡写真を示す。倍率は１８０倍である（右下点線の範囲が２５０μｍ）。不織布を構成する繊維の少なくとも一部が扁平化しているのが判る。 FIG. 1 shows an electron micrograph of the nonwoven fabric structure after wet papermaking according to one embodiment of the present invention. The magnification is 180 times (the range of the lower right dotted line is 250 μm). It can be seen that at least some of the fibers constituting the nonwoven fabric are flattened.
また、熱処理温度は、前記熱接着性繊維以外の繊維が溶融する温度より低い温度で熱処理することが好ましい。熱接着性繊維以外の繊維の溶融する温度を超えると、空隙が閉塞されて、比表面積が減少する恐れがあるからである。例えば、熱接着性繊維として、鞘成分を低融点ポリオレフィン樹脂とし、芯成分を鞘成分の融点より１０℃以上高い融点を有する高融点ポリオレフィン樹脂としたポリオレフィン鞘芯型複合繊維を用い、極細繊維をポリオレフィン鞘芯型複合繊維の鞘成分の融点より１０℃以上高い融点を有するポリオレフィン樹脂とした場合、熱処理温度は鞘成分の融点以上、芯成分及びポリオレフィン極細短繊維の融点より１０℃低い温度以下とすることが好ましい。 Moreover, it is preferable to heat-process the heat processing temperature at the temperature lower than the temperature at which fibers other than the said thermoadhesive fiber melt. This is because if the temperature at which the fibers other than the heat-adhesive fibers are melted is exceeded, the voids are blocked and the specific surface area may be reduced. For example, as the heat-adhesive fiber, a polyolefin sheath-core composite fiber in which the sheath component is a low-melting polyolefin resin and the core component is a high-melting polyolefin resin having a melting point higher by 10 ° C. than the melting point of the sheath component is used. When a polyolefin resin having a melting point higher by 10 ° C. or higher than the melting point of the sheath component of the polyolefin sheath-core composite fiber is used, the heat treatment temperature is not lower than the melting point of the sheath component and not more than 10 ° C. lower than the melting point of the core component and the polyolefin ultrafine fiber. It is preferable to do.
次いで、繊維ウェブ、特に前記湿式抄紙に水流交絡処理を施して繊維同士を交絡することが好ましい。前記極細繊維として分割型複合繊維を用いる場合、水流交絡処理により十分に割繊されていない分割型複合繊維を割繊して極細繊維が形成される。さらに主として不織布表面近傍の繊維が解かれて再配列される。水流交絡処理は、孔径０．０５ｍｍ以上０．５ｍｍ以下の範囲にあるオリフィスが０．３ｍｍ以上１．５ｍｍ以下の間隔で設けられるノズルから、水圧２ＭＰａ以上１０ＭＰａ以下の範囲の水流を不織布の表裏にそれぞれ１回以上噴射するとよい。より好ましい水圧の下限は、３ＭＰａである。より好ましい水圧の上限は、８．５ＭＰａである。水圧を上記範囲とすることにより、不織布の厚み方向において過度に繊維が配向されることなく、主として不織布表面近傍において繊維が解かれて再配列される。そのため、フッ素ガス処理において反応物質が不織布表面近傍から適度に入り込み、不織布内部に滞留して、硫黄原子を含む官能基を不織布内部に導入し易くするものと推定する。例えば、前記湿式抄紙が熱接着性繊維により熱接着したものであれば、水流交絡処理により構成繊維を再配列させたとしても、熱接着された部分は完全に崩壊しないように処理するのが好ましい。 Next, it is preferable to hydroentangle the fiber web, particularly the wet papermaking, to entangle the fibers. When split-type composite fibers are used as the ultrafine fibers, the split-type composite fibers that are not sufficiently split by the hydroentanglement process are split to form ultrafine fibers. Furthermore, fibers near the surface of the nonwoven fabric are mainly unwound and rearranged. Hydroentanglement treatment is performed by applying a water flow in the range of 2 MPa or more and 10 MPa or less on the front and back of the nonwoven fabric from a nozzle in which orifices having a hole diameter of 0.05 mm or more and 0.5 mm or less are provided at intervals of 0.3 mm or more and 1.5 mm or less. It is good to inject at least once each. A more preferable lower limit of the water pressure is 3 MPa. A more preferable upper limit of the water pressure is 8.5 MPa. By setting the water pressure within the above range, the fibers are unwound and rearranged mainly in the vicinity of the nonwoven fabric surface without excessively orienting the fibers in the thickness direction of the nonwoven fabric. For this reason, it is presumed that in the fluorine gas treatment, the reactant enters moderately from the vicinity of the nonwoven fabric surface and stays inside the nonwoven fabric, thereby facilitating introduction of functional groups containing sulfur atoms into the nonwoven fabric. For example, if the wet papermaking is heat-bonded with heat-adhesive fibers, it is preferable to treat the heat-bonded portion so that it does not completely collapse even if the constituent fibers are rearranged by hydroentanglement treatment. .
水流交絡処理された不織布は、熱接着性繊維の融点未満の温度で熱処理して乾燥させるか、熱接着性繊維の融点以上の温度で熱処理して、熱接着性繊維を再度溶融させて構成する繊維同士を熱接着させるとよい。上記操作によって、水流交絡処理されてなる湿式不織布の比表面積は、適度な範囲に調整されるとともに、不織布の引張強さを維持することで、最終的に得られるセパレータ材料の引張強さを維持することができる。水流交絡処理後の熱処理は、得ようとするセパレータ材料の比表面積を決定する因子の一つであり、過度に熱接着性繊維を溶融させると比表面積が低下する、又は反応物質が不織布の内部まで入り込みにくくなる可能性があるため、熱接着性繊維の融点未満の温度で熱処理することがより好ましい。より好ましい水流交絡処理後の不織布の熱処理温度は、熱接着性繊維の融点より５℃以上低い温度である。 The hydroentangled nonwoven fabric is heat treated at a temperature lower than the melting point of the heat-adhesive fiber and dried, or heat treated at a temperature equal to or higher than the melting point of the heat-adhesive fiber, and the heat-adhesive fiber is melted again. It is preferable to thermally bond the fibers together. By the above operation, the specific surface area of the wet nonwoven fabric that is hydroentangled is adjusted to an appropriate range, and the tensile strength of the separator material that is finally obtained is maintained by maintaining the tensile strength of the nonwoven fabric. can do. The heat treatment after hydroentanglement is one of the factors that determine the specific surface area of the separator material to be obtained. If the heat-adhesive fiber is melted excessively, the specific surface area decreases, or the reactant is inside the nonwoven fabric. It is more preferable to heat-treat at a temperature lower than the melting point of the heat-adhesive fiber. The heat treatment temperature of the nonwoven fabric after the hydroentanglement treatment is more preferably 5 ° C. or lower than the melting point of the thermoadhesive fiber.
そして、前述の方法により得られる不織布は、フッ素ガス処理が施されて硫黄原子を含む官能基を付与される。 And the nonwoven fabric obtained by the above-mentioned method is given the functional group containing a sulfur atom by performing a fluorine gas process.
まず、密封が可能な反応器内に不織布をセットし、１×１０4Ｐａ（０．１atom）以上９．５×１０4Ｐａ（０．９５atom）以下の範囲の減圧下で亜硫酸含有ガスに接触させる。反応器内の亜硫酸含有ガスは、濃度が０．５vol％以上、１０vol％以下の範囲の亜硫酸ガスを含有する。好ましい亜硫酸ガス濃度は、１vol％以上である。好ましい亜硫酸ガス濃度は、５vol％以下である。亜硫酸ガス濃度が０．５vol％未満であると、不織布に十分な亜硫酸ガス成分を接触させることができず、１０vol％を超えると、フッ素ガス導入時、ガス同士の反応による発熱で反応器内の温度上昇が顕著になり安全性が問題となる恐れがある。 First, a non-woven fabric is set in a reactor that can be sealed, and contacted with a sulfurous acid-containing gas under reduced pressure in the range of 1 × 10 4 Pa (0.1 atom) to 9.5 × 10 4 Pa (0.95 atom). Let The sulfurous acid-containing gas in the reactor contains sulfurous acid gas having a concentration of 0.5 vol% or more and 10 vol% or less. A preferable sulfurous acid gas concentration is 1 vol% or more. A preferable sulfurous acid gas concentration is 5 vol% or less. When the concentration of sulfurous acid gas is less than 0.5 vol%, a sufficient amount of sulfurous acid gas component cannot be brought into contact with the nonwoven fabric. When the concentration exceeds 10 vol%, heat is generated in the reactor due to heat generated by the reaction between gases when fluorine gas is introduced. There is a possibility that the temperature rise becomes remarkable and the safety becomes a problem.
また、前記亜硫酸含有ガスには、急激な反応を抑制させるとともに、反応時の温度上昇を緩和させ、安全、かつ効率的に表面改質するために、濃度９０vol％以上、９９．５vol％以下の範囲の窒素ガスを含有することが好ましい。より好ましい窒素ガス濃度の下限は、９５vol％以上である。より好ましい窒素ガス濃度の上限は、９９vol％以下である。 The sulfurous acid-containing gas has a concentration of 90 vol% or more and 99.5 vol% or less in order to suppress an abrupt reaction and mitigate a temperature rise during the reaction and to perform surface modification safely and efficiently. It is preferable to contain a range of nitrogen gas. A more preferable lower limit of the nitrogen gas concentration is 95 vol% or more. A more preferable upper limit of the nitrogen gas concentration is 99 vol% or less.
前記亜硫酸含有ガスの調製手順としては、所望のガス濃度に調整する手段であれば特に限定はされず、例えば、亜硫酸ガスと窒素ガスを予め混合した混合ガスを用いる方法、あるいは窒素ガスを反応器内に所定量導入した後、最後に亜硫酸含有ガスを導入する方法が挙げられ、後者が亜硫酸ガス濃度の微妙な調整、反応時間の制御がしやすく都合が良い。具体的には、反応器内を１×１０2Ｐａ（０．００１atom）以上５×１０3Ｐａ（０．０５atom）以下の範囲に減圧し、次に窒素ガスを反応器内に５０vol％以上、９０vol%以下の範囲で導入する。次いで、窒素ガスで希釈された亜硫酸ガスを反応器内に導入してガスの調整を行う。このとき、１×１０4Ｐａ（０．１atom）以上９．５×１０4Ｐａ（０．９５atom）以下の範囲の減圧下となるように亜硫酸含有ガスを導入し、不織布と接触させる。前記導入時の亜硫酸ガス濃度は、１０vol％以上、２０vol％以下の範囲であることが好ましい。導入時の亜硫酸ガス濃度が１０vol％未満であると、反応器内を所望の亜硫酸ガス濃度に調製する際のガス濃度の調整に必要以上に時間を費やす傾向となり、工程性に劣る。導入時の亜硫酸ガス濃度が２０vol％を超えると、反応器内の亜硫酸ガスの拡散が悪くなる傾向となる。 The procedure for preparing the sulfurous acid-containing gas is not particularly limited as long as it is a means for adjusting to a desired gas concentration. For example, a method using a mixed gas in which sulfurous acid gas and nitrogen gas are mixed in advance, or nitrogen gas in a reactor A method of introducing a sulfurous acid-containing gas at the end after introducing a predetermined amount into the inside is convenient, and the latter is convenient because it is easy to finely adjust the concentration of sulfurous acid gas and control the reaction time. Specifically, the pressure in the reactor is reduced to a range of 1 × 10 2 Pa (0.001 atom) or more and 5 × 10 3 Pa (0.05 atom) or less, and then nitrogen gas is added to the reactor in an amount of 50 vol% or more. It introduces in the range of 90 vol% or less. Subsequently, sulfurous acid gas diluted with nitrogen gas is introduced into the reactor to adjust the gas. At this time, a sulfurous acid-containing gas is introduced and brought into contact with the nonwoven fabric so as to be under a reduced pressure in the range of 1 × 10 4 Pa (0.1 atom) to 9.5 × 10 4 Pa (0.95 atom). The sulfurous acid gas concentration at the time of introduction is preferably in the range of 10 vol% or more and 20 vol% or less. When the concentration of sulfurous acid gas at the time of introduction is less than 10 vol%, it tends to spend more time than necessary to adjust the gas concentration when the inside of the reactor is adjusted to a desired sulfurous acid gas concentration, resulting in poor processability. When the concentration of sulfurous acid gas at the time of introduction exceeds 20 vol%, the diffusion of sulfurous acid gas in the reactor tends to deteriorate.
不織布と亜硫酸含有ガスの反応条件は、反応温度は０℃以上、４０℃以下の範囲が好ましい。反応温度が０℃未満であると、亜硫酸ガスの液化の危険性があり、４０℃を超えると、過剰反応が起こる恐れがある。また、反応時間は、３０秒以上５時間以下の範囲が好ましい。なお、ここでいう反応時間とは、反応器内にガスが充填されて不織布の巻き出しを開始したときを開始時間とし、所望の回数の巻き返しが終了するまでに要した時間をいう。 As for the reaction conditions of the nonwoven fabric and the sulfurous acid-containing gas, the reaction temperature is preferably in the range of 0 ° C or higher and 40 ° C or lower. If the reaction temperature is less than 0 ° C, there is a risk of liquefaction of sulfurous acid gas, and if it exceeds 40 ° C, an excessive reaction may occur. The reaction time is preferably in the range of 30 seconds to 5 hours. The reaction time here refers to the time required to complete the desired number of rewinds, with the start time being the time when the reactor is filled with gas and the unwinding of the nonwoven fabric is started.
次いで、反応器内の亜硫酸含有ガスに加えて、フッ素含有ガスを導入して１０×１０4Ｐａ（１atom）まで圧力を戻し、不織布を亜硫酸ガスとフッ素ガスの混合ガスに接触させる。 Next, in addition to the sulfurous acid-containing gas in the reactor, a fluorine-containing gas is introduced to return the pressure to 10 × 10 4 Pa (1 atom), and the nonwoven fabric is brought into contact with a mixed gas of sulfurous acid gas and fluorine gas.
反応器内のフッ素含有ガスは、濃度が０．１vol％以上、１０vol％以下の範囲のフッ素ガスを含有する。好ましいフッ素ガス濃度の下限は、０．５vol％以上である。好ましいフッ素ガス濃度の上限は、５vol％以下である。フッ素ガス濃度が０．１vol％以下であると、十分な親水化処理がされにくく、フッ素ガス濃度が１０vol％を超えると、残亜硫酸ガスとの発熱反応が促進され安全性が問題となる恐れがある。 The fluorine-containing gas in the reactor contains fluorine gas having a concentration in the range of 0.1 vol% or more and 10 vol% or less. The minimum of the preferable fluorine gas concentration is 0.5 vol% or more. The upper limit of the preferable fluorine gas concentration is 5 vol% or less. If the fluorine gas concentration is 0.1 vol% or less, sufficient hydrophilization treatment is difficult, and if the fluorine gas concentration exceeds 10 vol%, an exothermic reaction with the residual sulfurous acid gas is promoted and safety may be a problem. is there.
また、前記フッ素含有ガスには、急激な反応を抑制させるとともに、反応時の温度上昇を緩和させ、安全、かつ効率的に表面改質するために、窒素ガスを含有することが好ましい。窒素ガス濃度は、前記残存亜硫酸ガス濃度とフッ素ガス濃度を所望の範囲に設定することで決定される。 In addition, the fluorine-containing gas preferably contains nitrogen gas in order to suppress a rapid reaction, reduce a temperature increase during the reaction, and perform surface modification safely and efficiently. The nitrogen gas concentration is determined by setting the residual sulfurous acid gas concentration and the fluorine gas concentration within desired ranges.
前記フッ素含有ガスの調製順序としては、所望のガス濃度に調整する手段であれば特に限定はされず、例えば、フッ素ガスと窒素ガスを予め混合した混合ガスを用いる方法、あるいは窒素ガスを反応器内に所定量導入した後、最後にフッ素含有ガスを導入する方法が挙げられ、後者が、あらかじめ窒素ガスの存在している雰囲気にフッ素含有混合ガスを導入するため、発熱反応が抑制され都合が良い。 The order of preparing the fluorine-containing gas is not particularly limited as long as it is a means for adjusting to a desired gas concentration. For example, a method using a mixed gas in which fluorine gas and nitrogen gas are mixed in advance, or nitrogen gas in a reactor A method of introducing a fluorine-containing gas at the end after a predetermined amount is introduced into the inside, and the latter introduces the fluorine-containing mixed gas into an atmosphere in which nitrogen gas is present in advance, which is advantageous in that an exothermic reaction is suppressed. good.
反応条件は、反応温度は０℃以上、４０℃以下の範囲が好ましい。反応温度が０℃未満であると、亜硫酸ガスの液化の危険性があり、４０℃を超えると、過剰反応が起こる恐れがある。また、反応時間は、３０秒以上５時間以下の範囲が好ましい。 As for the reaction conditions, the reaction temperature is preferably in the range of 0 ° C or higher and 40 ° C or lower. If the reaction temperature is less than 0 ° C, there is a risk of liquefaction of sulfurous acid gas, and if it exceeds 40 ° C, an excessive reaction may occur. The reaction time is preferably in the range of 30 seconds to 5 hours.
以上の操作により、亜硫酸ガスを減圧下で不織布に接触反応させ、前記亜硫酸ガスを残存させた状態でフッ素ガスを不織布に接触反応させるバッチ式多段処理を行う。 By the above operation, a batch-type multistage treatment is performed in which sulfurous acid gas is brought into contact with the nonwoven fabric under reduced pressure, and fluorine gas is brought into contact with the nonwoven fabric while the sulfurous acid gas remains.
前記フッ素ガス処理を完了した後、反応器内の残留ガスを排気口から排気し、窒素ガスなどで約１０×１０4Ｐa（約１atom）程度まで復圧して、表面改質された不織布は取り出される。このとき、必要に応じて、反応器内のフッ素残留ガスを５×１０4Ｐa（０．５atom）以下になるまで真空ポンプの吸引装置を用いて、反応器内を減圧しながら、排気口から反応器外に排気し、さらに、その減圧系に酸素含有ガスで復圧させて約１０×１０4Ｐａ（約１atom）程度まで復圧した後、前記酸素含有ガス中で不織布を処理することができる。前記処理を施すことにより、不織布の表面に残留した副生成物であるフッ酸（ＨＦ）の除去や、残留フッ素ガス成分を置換の効果がある。前記酸素含有ガスは、酸素ガスのみであってもよいし、窒素ガスを含有していてもよい。窒素ガスと酸素ガスの混合比率としては、特に限定するものではなく、前記効果が期待できる量の酸素ガスが含まれていればよい。 After the fluorine gas treatment is completed, the residual gas in the reactor is exhausted from the exhaust port, the pressure is restored to about 10 × 10 4 Pa (about 1 atom) with nitrogen gas, etc., and the surface-modified nonwoven fabric is taken out. It is. At this time, if necessary, from the exhaust port while reducing the pressure in the reactor using a vacuum pump suction device until the residual fluorine gas in the reactor becomes 5 × 10 4 Pa (0.5 atom) or less. After exhausting the reactor, the decompression system is decompressed with an oxygen-containing gas and decompressed to about 10 × 10 4 Pa (about 1 atom), and then the nonwoven fabric is treated in the oxygen-containing gas. it can. By performing the treatment, there is an effect of removing hydrofluoric acid (HF), which is a by-product remaining on the surface of the nonwoven fabric, and replacing the residual fluorine gas component. The oxygen-containing gas may be only oxygen gas or may contain nitrogen gas. The mixing ratio of the nitrogen gas and the oxygen gas is not particularly limited as long as the oxygen gas is contained in an amount that can expect the above effect.
以上のようにして表面改質された不織布は、反応器外に取り出される。前記表面改質された不織布は、表面に残留フッ酸や、フッ素ガスで分解された低分子量成分が微量に残存している恐れがあるため、アルカリ洗浄処理、温水洗浄処理、乾燥処理が施される。 The nonwoven fabric surface-modified as described above is taken out of the reactor. The surface-modified nonwoven fabric is subjected to alkali cleaning treatment, hot water cleaning treatment, and drying treatment because there is a possibility that trace amounts of residual hydrofluoric acid and low molecular weight components decomposed with fluorine gas may remain on the surface. The
以上説明のとおり、従来の混合ガス法で極細繊維を用いるなどした緻密な不織布を処理すると、硫黄含有官能基が不織布表面に集中して、不織布全体からすると表面に偏在していたが、本発明のバッチ式多段処理方法を採ることにより、不織布内部にまで硫黄含有官能基を付与することができる。 As described above, when processing a dense nonwoven fabric using ultrafine fibers by the conventional mixed gas method, the sulfur-containing functional groups are concentrated on the nonwoven fabric surface, and the entire nonwoven fabric was unevenly distributed on the surface. By adopting the batch-type multistage treatment method, a sulfur-containing functional group can be imparted to the inside of the nonwoven fabric.
そして、前記不織布は、カレンダーロール等で加圧して厚みを調整するとよい。 And the said nonwoven fabric is good to pressurize with a calender roll etc. and to adjust thickness.
以下、本発明の内容について実施例を挙げて説明する。なお、繊維の融点、単繊維強度、セパレータ材料の厚み、不織布の比表面積、分割型複合繊維の割繊率、有効硫黄原子量、及び平均孔径は、以下の方法により測定した。
［融点］
ＪＩＳ Ｋ ７１２１（ＤＳＣ法）に準じ測定した。
［単繊維強度］
ＪＩＳ Ｌ １０１５に準じ、引張試験機を用いて、試料の掴み間隔を２０ｍｍとし、繊維が切断したときの荷重値を測定し単繊維強度とした。
［セパレータ材料の厚み］
１７５ｋＰａ荷重（ＪＩＳ−Ｂ−７５０２に準じたマイクロメーターによる測定）により、３枚の試料のそれぞれ異なる１０箇所で厚みを測定し、計３０箇所の平均値を求めた。
［不織布の比表面積］
比表面積計（トライスター３０００形、（株）島津製作所製）を用いて測定した。不織布を３ｃｍ×８ｃｍ角に切断した後、測定セルに採る。温度６０℃で２時間脱ガス処理した後、窒素ガスを用いた多点ＢＥＴ法で測定した。
［割繊率］
不織布の長手方向が断面となるように束ねて１ｍｍ径の穴のあいた金属プレートに通し、電子顕微鏡を用いて４００倍に拡大して、割繊された極細繊維の割合を算出して求めた。
［電子分光法（ＥＳＣＡ）］
Ｘ線光電子分光計（ＰＥＲＫＩＮ ＥＬＭＡＲ製 アルバックファイＥＳＣＡ５５００ＭＴ）を用いて、励起源としてＭｇ−Ｋα線、印加電圧を１５ｋｖ、ビーム電流値を１０ｍＡ、Ｘ線取り出し角度を４５度及び７５度として、不織布表面から炭素原子、フッ素原子、硫黄原子、及び酸素原子のそれぞれのピーク面積を測定し、光イオン化断面積補正をして、炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比を測定した。測定面積は８００μｍφで測定した。
［フラスコ燃焼法］
（１）吸収液の調製
ＮａＨＣＯ3８４ｍｇを純水１００ｍｌに溶かし、３１％Ｈ2Ｏ2溶液を１ｍｌ加え、吸収液を調製した。
（２）試料の調製
不織布から試料１ｇを採取し、１３％水酸化カリウム水溶液に３０分間浸漬する。しかる後に水道水で３０分間洗浄し、さらに純水で３０分間洗浄する。次いで、６０℃で１時間乾燥して試料を調製した。
（３）酸素燃焼フラスコ法
燃焼フラスコ内に前記吸収液５ｍｌを入れ、内壁を純水で濡らす。次に、前記試料を２０ｍｇ精秤し、無灰濾紙（５Ｃ）に包み白金籠にセットした後、フラスコ内を酸素で３０秒間満たす。しかる後に、白金籠に通電（引火）し試料を燃焼させる。燃焼後は、時折フラスコ注液部に純水を注ぎ足しながらよく振り、５分間冷却する。冷却後、注液部の純水により内壁を洗浄し数分間放置する。燃焼フラスコの吸収液をメスフラスコで５０ｍｌに定容し、測定溶液を採取した。
（４）（Ｓ／Ｃ）Bの測定
イオンクロマト装置（ＤＩＯＮＥＸ製、ＤＸ−１００）を用い、前記測定溶液のＳＯ4 2-濃度を測定し、ＳＯ4 2-濃度と試料質量から（Ｓ／Ｃ）Bを算出した。
［有効硫黄原子量］
自己放電抑制効果を確認する代用特性として、有効硫黄原子量を下記式（１）で算出した。
Hereinafter, the contents of the present invention will be described with reference to examples. The melting point of the fiber, the single fiber strength, the thickness of the separator material, the specific surface area of the nonwoven fabric, the splitting rate of the split-type composite fiber, the effective sulfur atom amount, and the average pore diameter were measured by the following methods.
[Melting point]
It measured according to JISK7121 (DSC method).
[Single fiber strength]
In accordance with JIS L 1015, using a tensile tester, the gripping interval of the sample was 20 mm, the load value when the fiber was cut was measured, and the single fiber strength was obtained.
[Thickness of separator material]
The thickness was measured at 10 different points of each of the three samples with a 175 kPa load (measured with a micrometer according to JIS-B-7502), and the average value of a total of 30 points was determined.
[Specific surface area of non-woven fabric]
Measurement was performed using a specific surface area meter (Tristar 3000 type, manufactured by Shimadzu Corporation). The nonwoven fabric is cut into a 3 cm × 8 cm square and then taken into a measurement cell. After degassing treatment at a temperature of 60 ° C. for 2 hours, measurement was performed by a multipoint BET method using nitrogen gas.
[Split rate]
The nonwoven fabric was bundled so that the longitudinal direction was a cross-section, passed through a metal plate having a 1 mm diameter hole, magnified 400 times using an electron microscope, and the ratio of the split ultrafine fibers was calculated.
[Electron Spectroscopy (ESCA)]
Using an X-ray photoelectron spectrometer (ULKIN Phi ESCA5500MT manufactured by PERKIN ELMAR), Mg-Kα ray as an excitation source, applied voltage of 15 kv, beam current value of 10 mA, X-ray extraction angles of 45 degrees and 75 degrees, and nonwoven fabric surface Then, the peak areas of carbon atoms, fluorine atoms, sulfur atoms, and oxygen atoms were measured, the photoionization cross section was corrected, and the ratio of the number of sulfur atoms (S) to the number of carbon atoms (C) was measured. The measurement area was measured at 800 μmφ.
[Flask combustion method]
(1) Preparation of Absorbing Solution 84 mg of NaHCO 3 was dissolved in 100 ml of pure water, and 1 ml of 31% H 2 O 2 solution was added to prepare an absorbing solution.
(2) Preparation of sample 1 g of a sample is taken from the nonwoven fabric and immersed in a 13% aqueous potassium hydroxide solution for 30 minutes. Thereafter, it is washed with tap water for 30 minutes and further washed with pure water for 30 minutes. Subsequently, it dried at 60 degreeC for 1 hour, and prepared the sample.
(3) Oxygen combustion flask method 5 ml of the absorbent is put into a combustion flask, and the inner wall is wetted with pure water. Next, 20 mg of the sample is precisely weighed, wrapped in ashless filter paper (5C) and set in a platinum cage, and then the flask is filled with oxygen for 30 seconds. After that, energize (ignite) the platinum soot and burn the sample. After combustion, occasionally shake pure water while pouring pure water into the flask pouring part and cool for 5 minutes. After cooling, the inner wall is washed with pure water in the liquid injection part and left for several minutes. The absorbent in the combustion flask was made up to a volume of 50 ml with a measuring flask, and the measurement solution was collected.
(4) (S / C) Measurement of B Using an ion chromatograph (made by DIONEX, DX-100), the SO 4 2− concentration of the measurement solution was measured, and the SO 4 2− concentration and the sample mass (S / C) were measured. C) B was calculated.
[Effective sulfur atomic weight]
As a substitute characteristic for confirming the self-discharge suppression effect, the effective sulfur atom amount was calculated by the following formula (1).
有効硫黄原子量＝（Ｓ／Ｃ）B×［（Ｓ／Ｃ）E／（Ｓ／Ｃ）E75］・・・（１）
自己放電抑制に効果があるとされるスルホン基等の硫黄含有官能基は、不織布全体に導入されるほど電池内で有効に作用する。また、各々の繊維については、繊維内部に対して繊維表面に多く導入されるほど電池内で有効に作用する。上記式（１）において、（Ｓ／Ｃ）Bは不織布全体に導入された硫黄原子量を指し、［（Ｓ／Ｃ）E／（Ｓ／Ｃ）E75］は繊維表面に導入された硫黄原子量を指し、これを乗じて電池内で有効に作用する硫黄含有官能基を硫黄原子量に置き換えて求めることとした。有効硫黄原子量の値が大きいほど、自己放電抑制効果が高いとした。
［平均孔径］
耐ショート性効果を確認する代用特性として、平均孔径を用いた。平均孔径は、パームポロメータ(Ｐｏｒｏｕｓ Ｍａｔｅｒｉａｌｓ Ｉｎｃ．製)を使用し、ＡＳＴＭ Ｆ ３１６ ８６に準じ、バブルポイント法によって測定した。平均孔径が小さいほど、耐ショート性が高いとした。
Effective sulfur atom amount = (S / C) B × [(S / C) E / (S / C) E75 ] (1)
A sulfur-containing functional group such as a sulfone group, which is said to be effective in suppressing self-discharge, works more effectively in the battery as it is introduced into the entire nonwoven fabric. Moreover, about each fiber, the more it introduce | transduces on the fiber surface with respect to the inside of a fiber, it acts effectively in a battery. In the above formula (1), (S / C) B indicates the amount of sulfur atoms introduced into the entire nonwoven fabric, and [(S / C) E / (S / C) E75 ] indicates the amount of sulfur atoms introduced on the fiber surface. By multiplying this, the sulfur-containing functional group that works effectively in the battery was replaced with the sulfur atom weight. The greater the effective sulfur atom value, the higher the self-discharge suppression effect.
[Average pore size]
As a substitute characteristic for confirming the short-circuit resistance effect, the average pore diameter was used. The average pore diameter was measured by a bubble point method using a palm porometer (manufactured by Porous Materials Inc.) according to ASTM F31686. The smaller the average pore diameter, the higher the short circuit resistance.
実施例及び比較例に用いられる繊維原料を以下のとおり準備した。
［繊維１］第１成分：ポリプロピレン、第２成分：エチレン−ビニルアルコール共重合体からなる繊度１．４ｄｔｅｘ、繊維長６ｍｍ、放射状１６分割型複合繊維（大和紡績（株）製、ＤＦ−２）。割繊後の平均繊維径は約３．２μｍ（割繊後の繊度は約０．０８７５ｄｔｅｘ）。
［繊維２］第１成分：ポリプロピレン、第２成分：エチレン−ビニルアルコール共重合体からなる繊度３．３ｄｔｅｘ、繊維長６ｍｍ、放射状１６分割型複合繊維（大和紡績（株）製、ＤＦ−２）。割繊後の平均繊維径は約５μｍ（割繊後の繊度は約０．２ｄｔｅｘ）。
［繊維３］芯成分：ポリプロピレン、鞘成分：高密度ポリエチレンからなる繊度１．７ｄｔｅｘ、繊維長１０ｍｍの芯鞘型複合繊維（大和紡績（株）製、ＮＢＦ（Ｈ））。繊維径は約１５．２μｍ。
［繊維４］ポリプロピレンからなる繊度２．２ｄｔｅｘ、繊維長１０ｍｍ、繊維強度６ｃＮ／ｄｔｅｘの単一繊維（大和紡績（株）製、ＰＺ）。繊維径は約１７．５μｍ。
［実施例１〜２］
表１に示す繊維配合で混合して０．５ｍａｓｓ％の濃度になるように水分散スラリーを調製し、パルパーを用い撹拌時間６０ｍｉｎ、回転数１０００ｒｐｍで繊維１に割繊処理を施した。得られた水分散スラリーを円網式湿式抄紙機及び短網式湿式抄紙機からそれぞれ目付約２０ｇ／ｍ2の湿式抄紙ウェブを作製して抄き合わせた。次いでシリンダードライヤー機を用いて、線圧４０Ｎ／ｃｍ、温度１３５℃で熱処理を施して、繊維３の鞘成分を溶融させて構成する繊維同士を接着させて湿式抄紙を得た。この湿式抄紙は、構成する繊維の一部が扁平化されていた。
The fiber raw material used for an Example and a comparative example was prepared as follows.
[Fiber 1] 1st component: Polypropylene, 2nd component: Fineness 1.4dtex made of ethylene-vinyl alcohol copolymer, fiber length 6mm, radial 16 split type composite fiber (Daiwabo Co., Ltd., DF-2) . The average fiber diameter after splitting is about 3.2 μm (the fineness after splitting is about 0.0875 dtex).
[Fiber 2] First component: Polypropylene, Second component: Fineness 3.3dtex composed of ethylene-vinyl alcohol copolymer, fiber length 6 mm, radial 16-split composite fiber (Daiwabo Co., Ltd., DF-2) . The average fiber diameter after splitting is about 5 μm (the fineness after splitting is about 0.2 dtex).
[Fiber 3] Core component: polypropylene, sheath component: core-sheath type composite fiber having a fineness of 1.7 dtex and a fiber length of 10 mm made of high-density polyethylene (manufactured by Daiwabo Co., Ltd., NBF (H)). The fiber diameter is about 15.2 μm.
[Fiber 4] A single fiber made of polypropylene having a fineness of 2.2 dtex, a fiber length of 10 mm, and a fiber strength of 6 cN / dtex (manufactured by Yamatobo Co., Ltd., PZ). The fiber diameter is about 17.5 μm.
[Examples 1-2]
An aqueous dispersion slurry was prepared by mixing with the fiber composition shown in Table 1 to a concentration of 0.5 mass%, and the fiber 1 was split using a pulper with a stirring time of 60 min and a rotation speed of 1000 rpm. The obtained water-dispersed slurry was made from a circular mesh wet paper machine and a short mesh wet paper machine, respectively, and wet paper webs having a basis weight of about 20 g / m 2 were prepared and combined. Next, using a cylinder dryer, heat treatment was performed at a linear pressure of 40 N / cm and a temperature of 135 ° C. to melt the sheath component of the fibers 3 to bond the constituent fibers to obtain wet papermaking. In this wet papermaking, some of the constituent fibers were flattened.
次に、前記湿式抄紙に、孔径０．１ｍｍのオリフィスが０．６ｍｍの間隔で設けられたノズルから水圧３ＭＰａ、４ＭＰａ、８ＭＰａの柱状水流を不織布の表側及び裏側にそれぞれ噴射して、水流交絡処理を施した。次いで、熱風ドライヤーを用いて１３０℃で乾燥して、水流交絡処理された湿式不織布を得た。前記湿式不織布において繊維１は、約９５％が割繊してエチレン−ビニルアルコール極細繊維及びポリプロピレン極細繊維が発現していた。 Next, a water flow entanglement treatment is carried out by spraying a columnar water flow of water pressure 3 MPa, 4 MPa, and 8 MPa to the front side and the back side of the nonwoven fabric from a nozzle provided with orifices having a hole diameter of 0.1 mm at intervals of 0.6 mm on the wet papermaking. Was given. Subsequently, it dried at 130 degreeC using the hot air dryer, and obtained the wet nonwoven fabric by which the hydroentanglement process was carried out. In the wet nonwoven fabric, about 95% of the fibers 1 were split, and ethylene-vinyl alcohol ultrafine fibers and polypropylene ultrafine fibers were developed.
次に、反応器内に湿式抄紙からなる不織布を入れ、まず１．３×１０3Ｐａ（０．０１３atom）に真空脱気した。次にＮ2ガスを導入して圧力を５．８×１０4Ｐａ（０．５８atom）とし、その後、亜硫酸ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を９×１０4Ｐａ（０．９atom）とした。この状態で約１００分間反応させた。このとき、反応器内の亜硫酸ガス／Ｎ2ガスの混合ガスの濃度は、約３．６vol％／約９６．４vol％であった。
Next, a nonwoven fabric made of wet papermaking was placed in the reactor, and first vacuum degassed to 1.3 × 10 3 Pa (0.013 atom). Next, N 2 gas is introduced to a pressure of 5.8 × 10 4 Pa (0.58 atom), and then a mixed gas of
次にフッ素ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を１×１０5Ｐａ（１atom、大気圧）とした。この状態で約１００分間反応させた。この反応は、亜硫酸ガスとフッ素ガスが共存した状態における反応である。また、反応器内のフッ素ガス濃度は、１vol％であった。 Next, a mixed gas of 10 vol% fluorine gas / 90 vol% N 2 gas was introduced, and the pressure in the reactor was set to 1 × 10 5 Pa (1 atom, atmospheric pressure). In this state, the reaction was performed for about 100 minutes. This reaction is a reaction in a state where sulfurous acid gas and fluorine gas coexist. Moreover, the fluorine gas concentration in the reactor was 1 vol%.
その後、脱気して反応器内圧力を５×１０4Ｐａ（０．５atom）とし、次に酸素ガスを導入して反応器内圧力を１×１０5Ｐａ（１atom、大気圧）とした。この状態で約３０分間反応させた。 Thereafter, deaeration was performed to set the internal pressure of the reactor to 5 × 10 4 Pa (0.5 atom), and oxygen gas was then introduced to adjust the internal pressure of the reactor to 1 × 10 5 Pa (1 atom, atmospheric pressure). It was made to react for about 30 minutes in this state.
次に１．３×１０3Ｐａ（０．０１３atom）に真空脱気し、その後Ｎ2ガスを導入して大気圧に戻した。以上の操作は、一つの反応器を用いたバッチ式で行った。 Next, vacuum degassing was performed to 1.3 × 10 3 Pa (0.013 atom), and then N 2 gas was introduced to return to atmospheric pressure. The above operation was performed in a batch system using one reactor.
以上の操作により、亜硫酸ガスを減圧下で不織布に接触反応させ、前記亜硫酸ガスを残存させた状態でフッ素ガスを不織布に接触反応させるバッチ式多段処理を行った。 By the above operation, a batch-type multistage treatment was performed in which sulfurous acid gas was brought into contact with the nonwoven fabric under reduced pressure, and fluorine gas was brought into contact with the nonwoven fabric with the sulfurous acid gas remaining.
前記親水化処理後、温度６０℃、濃度２．５％のＫＯＨ溶液で不織布を洗浄し、熱風ドライヤーを用いて７５℃で乾燥した。次いで、不織布をロール温度６０℃、線圧８００Ｎ／ｃｍのカレンダーロールを用いてカレンダー処理を施して、厚みを調整し、本発明のセパレータ材料を得た。
［比較例１〜３］
表１に示す繊維配合で混合した以外は、実施例１と同様の方法で水流交絡処理された湿式不織布を作製した。なお、比較例３は、分割型複合繊維を用いていないので、パルパーの使用、および水流交絡処理を省略した。
（１）比較例１の親水化処理条件
反応器内に湿式抄紙からなる不織布を入れ、まず１．３×１０3Ｐａ（０．０１３atom）に真空脱気した。次にＮ2ガスを導入して圧力を９×１０4Ｐａ（０．９atom）とし、その後、亜硫酸ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を１×１０5Ｐａ（１atom、大気圧）とした。この状態で約１００分間反応させた。このとき、反応器内の亜硫酸ガス／Ｎ2ガスの混合ガスの濃度は、１vol％／９９vol％であった。
After the hydrophilization treatment, the nonwoven fabric was washed with a KOH solution having a temperature of 60 ° C. and a concentration of 2.5%, and dried at 75 ° C. using a hot air dryer. Next, the nonwoven fabric was calendered using a calender roll having a roll temperature of 60 ° C. and a linear pressure of 800 N / cm to adjust the thickness, thereby obtaining the separator material of the present invention.
[Comparative Examples 1-3]
A wet nonwoven fabric subjected to hydroentanglement treatment was prepared in the same manner as in Example 1 except that the fiber blending shown in Table 1 was mixed. Since Comparative Example 3 does not use split-type conjugate fibers, the use of a pulper and hydroentanglement treatment were omitted.
(1) Hydrophilization treatment conditions of Comparative Example 1 A nonwoven fabric made of wet papermaking was placed in the reactor, and first vacuum degassed to 1.3 × 10 3 Pa (0.013 atom). Next, N 2 gas is introduced to adjust the pressure to 9 × 10 4 Pa (0.9 atom), and then a mixed gas of
次に真空脱気し、容器内圧力を７．６×１０4Ｐａ（０．７６atom）にし、その後Ｎ2ガスを導入して圧力を９．６×１０4Ｐａ（０．９６atom）とした。次にフッ素ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を１×１０5Ｐａ（１atom、大気圧）とした。この状態で約１００分間反応させた。このとき、反応器内のフッ素ガス濃度は、０．４vol％であった。
その後は実施例１〜２と同一条件とした。
Next, vacuum evacuation was performed, the internal pressure of the container was set to 7.6 × 10 4 Pa (0.76 atom), and then N 2 gas was introduced to adjust the pressure to 9.6 × 10 4 Pa (0.96 atom). Next, a mixed gas of 10 vol% fluorine gas / 90 vol% N 2 gas was introduced, and the pressure in the reactor was set to 1 × 10 5 Pa (1 atom, atmospheric pressure). In this state, the reaction was performed for about 100 minutes. At this time, the fluorine gas concentration in the reactor was 0.4 vol%.
Thereafter, the same conditions as in Examples 1 and 2 were used.
以上の操作は、一つの反応器を用いたバッチ式で行った。
（２）比較例２及び３の親水化処理条件
反応器内に不織布を入れ、まず１．３×１０3Ｐａ（０．０１３atom）に真空脱気した。次にＮ2ガスを導入して圧力を８×１０3Ｐａ（０．０８atom）とし、その後、亜硫酸ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を４×１０4Ｐａ（０．４atom）とした。さらに、フッ素ガス１０vol％／Ｎ2ガス９０vol％の混合ガスを導入し、反応器内圧力を５×１０4Ｐａ（０．５atom）とした後、酸素ガスを１×１０5Ｐａ（１atom、大気圧）になるまで導入した。この状態で約２００分間反応させた。このとき、反応器内の亜硫酸ガス／フッ素ガス／酸素ガス／Ｎ2ガスの混合ガスの濃度は、約３．２vol％／約１．１vol％／約５０vol％／約４５．７vol％であった。
The above operation was performed in a batch system using one reactor.
(2) Hydrophilization treatment conditions of Comparative Examples 2 and 3 A nonwoven fabric was placed in the reactor and first vacuum degassed to 1.3 × 10 3 Pa (0.013 atom). Next, N 2 gas is introduced to make the pressure 8 × 10 3 Pa (0.08 atom), and then a mixed gas of 10 vol% sulfurous acid gas / 90 vol% N 2 gas is introduced, and the pressure in the reactor is 4 × 10 10 The pressure was 4 Pa (0.4 atom). Furthermore, after introducing a mixed gas of 10 vol% fluorine gas / 90 vol% N 2 gas and setting the pressure in the reactor to 5 × 10 4 Pa (0.5 atom), oxygen gas was 1 × 10 5 Pa (1 atom, large). It was introduced until atmospheric pressure). It was made to react for about 200 minutes in this state. At this time, the concentration of the mixed gas of sulfurous acid gas / fluorine gas / oxygen gas / N 2 gas in the reactor was about 3.2 vol% / about 1.1 vol% / about 50 vol% / about 45.7 vol%. .
その後、１．３×１０3Ｐａ（０．０１３atom）まで真空脱気し、その後Ｎ2ガスを導入して１×１０5Ｐａ（１atom、大気圧）に戻した。その後は実施例１〜２と同一条件とした。 Thereafter, vacuum degassing was performed to 1.3 × 10 3 Pa (0.013 atom), and then N 2 gas was introduced to return to 1 × 10 5 Pa (1 atom, atmospheric pressure). Thereafter, the same conditions as in Examples 1 and 2 were used.
以上の操作は、一つの反応器を用いたバッチ式で行った。 The above operation was performed in a batch system using one reactor.
以上の条件と結果を表１に示す。
The above conditions and results are shown in Table 1.
以上の結果から、実施例１及び２のセパレータ材料は、４μｍ未満の極細繊維を含有し、不織布の表面及び内部に所望の硫黄含有官能基を付与されていたため、耐ショート性の指標である平均孔径が小さく緻密な構造を有しながらも、電池内での電解液の偏在を抑制することが可能なセパレータが得られた。さらに、実施例１及び２のセパレータ材料は、繊維表面に硫黄含有官能基が集中的に付与されていたので、自己放電抑制効果の指標である有効硫黄原子量が高い値を示していた。 From the above results, since the separator materials of Examples 1 and 2 contained ultrafine fibers of less than 4 μm and were given desired sulfur-containing functional groups on the surface and inside of the nonwoven fabric, the average is an index of short-circuit resistance A separator capable of suppressing the uneven distribution of the electrolyte in the battery while having a small pore size and a dense structure was obtained. Furthermore, since the separator material of Examples 1 and 2 had sulfur-containing functional groups concentrated on the fiber surface, the effective sulfur atom amount, which is an index of the self-discharge suppression effect, showed a high value.
一方、比較例１及び２は、緻密な構造を有する不織布であったが不織布内部まで十分にフッ素ガス処理することができず、繊維内部に反応が進んだため、自己放電抑制効果の指標である有効硫黄原子量が低い値を示していた。また、比較例３は、極細繊維を使用しないため、不織布の緻密性が低く耐ショート性の指標である平均孔径が大きいだけでなく、繊維内部に反応が進んだため、自己放電抑制効果の指標である有効硫黄原子量が低い値を示していた。 On the other hand, Comparative Examples 1 and 2 were non-woven fabrics having a dense structure, but they could not be sufficiently treated with fluorine gas to the inside of the non-woven fabric, and the reaction proceeded inside the fibers, which is an index of the self-discharge suppression effect. The effective sulfur atom amount was low. In addition, since Comparative Example 3 does not use ultrafine fibers, the non-woven fabric has a low density and not only a large average pore diameter, which is an indicator of short-circuit resistance. The effective sulfur atomic weight was low.
本発明のセパレータ材料は、アルカリ二次電池、リチウムイオン二次電池、電気二重層キャパシタ、コンデンサー等の電気化学素子、又はイオン交換セパレータ（イオンキャッチャー）等に用いられるセパレータ材料に関する。特に、ニッケル−カドミウム電池、ニッケル−亜鉛電池、ニッケル−水素電池等のアルカリ二次電池用途において、電解液保持性が高く、耐ショート性が高く、電池の内部抵抗抑制効果及び自己放電抑制効果が高いセパレータ材料として好適である。また、本発明のアルカリ二次電池用セパレータは、携帯電話、デジタル（ビデオ）カメラ、ノート型パソコンなどの一般民生用電池等に好適である。 The separator material of the present invention relates to a separator material used for an alkaline secondary battery, a lithium ion secondary battery, an electric double layer capacitor, an electrochemical element such as a capacitor, or an ion exchange separator (ion catcher). In particular, in alkaline secondary battery applications such as nickel-cadmium batteries, nickel-zinc batteries, nickel-hydrogen batteries, etc., the electrolyte retention is high, the short circuit resistance is high, and the internal resistance suppression effect and self-discharge suppression effect of the battery are high. Suitable as a high separator material. The separator for alkaline secondary batteries of the present invention is suitable for general consumer batteries such as mobile phones, digital (video) cameras, and notebook computers.
Claims (10)
前記不織布は、電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対するフッ素原子数（Ｆ）の比（Ｆ／Ｃ）が、１×１０-2以上２０×１０-2以下の範囲内にあり、前記不織布は、下記（１）〜（３）を満たすことを特徴とするセパレータ材料。
（１）電子分光法（ＥＳＣＡ）を用いてＸ線取り出し角４５度により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Eが、１×１０-2以上１０×１０-2以下の範囲内にある。
（２）前記不織布は、フラスコ燃焼法により測定される炭素原子数（Ｃ）に対する硫黄原子数（Ｓ）の比（Ｓ／Ｃ）Bが、０．１×１０-3以上０．５×１０-3以下の範囲内にある。
（３）前記（Ｓ／Ｃ）Eと（Ｓ／Ｃ）Bの比［（Ｓ／Ｃ）E／（Ｓ／Ｃ）B］が、１００以上２５０以下の範囲内にある。 A separator material composed of a non-woven fabric including an ultrafine fiber having a fiber diameter of 4 μm or less and a heat-adhesive fiber , wherein at least a part of the heat-adhesive fiber is flattened,
The nonwoven fabric has a ratio (F / C) of the number of fluorine atoms (F) to the number of carbon atoms (C) measured by electron spectroscopy (ESCA) with an X-ray extraction angle of 45 degrees is 1 × 10 −2. The separator material, which is in the range of 20 × 10 −2 or less and the nonwoven fabric satisfies the following (1) to (3).
(1) Ratio (S / C) of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by an electron spectroscopy (ESCA) with an X-ray extraction angle of 45 degrees E is 1 × 10 −2 It is in the range of 10 × 10 −2 or less.
(2) The nonwoven fabric has a ratio (S / C) B of the number of sulfur atoms (S) to the number of carbon atoms (C) measured by a flask combustion method of 0.1 × 10 −3 or more and 0.5 × 10 -3 or less.
(3) the (S / C) E and (S / C) ratio of B [(S / C) E / (S / C) B] is in the range of 100 to 250 or less.
不活性ガス雰囲気下、減圧に保持した状態で亜硫酸含有ガスを前記反応器に導入して前記繊維ウェブまたは前記不織布を巻き出しながら繊維表面と接触反応させ、
前記亜硫酸含有ガスが存在する状態でフッ素含有ガスを前記反応器に導入して、前記亜硫酸含有ガスと前記フッ素含有ガスの混合ガスを繊維表面と接触反応させることを特徴とするセパレータ材料の製造方法。 Fiber diameter saw contains the following ultrafine fibers and the thermally adhesive fiber 4 [mu] m, the fiber web or nonwoven least part of the thermal bonding fibers are flattened and placed in a sealed reactor,
In an inert gas atmosphere, a sulfurous acid-containing gas is introduced into the reactor while maintaining a reduced pressure, and the fiber surface or the nonwoven fabric is brought into contact with the fiber surface while being unwound .
A method for producing a separator material, wherein a fluorine-containing gas is introduced into the reactor in the presence of the sulfurous acid-containing gas, and a mixed gas of the sulfurous acid-containing gas and the fluorine-containing gas is brought into contact with a fiber surface. .
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